You are so powerful actually that you are scared of yourself.
There are three ‘you’s in that statement. The first two refer to the small self or the ego. The third one refers to the best that you can be, the Great Self, the Truth—classically, the Ātman . And classically the first two ‘you’s refer to aham , the ego. The third one refers to, you could say, the dissolved ego, the ascended ego, the purified ego.
So, the ego is afraid of its own betterment. In the case of the ego, betterment is not about getting bigger; betterment implies getting smaller. And the ego does not want to get smaller. Who wants to get smaller? Nobody. So, therefore the scare.